Phosphodiesterase (PDE) denotes a species of proteases, and is capable of selectively degrading the second massagers, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in human bodies to the corresponding adenosine monophosphates to exert important physiological functions. Till now, 11 families of phosphodiesterases have been reported, wherein the phosphodiesterase IX (PDEIX) is capable of hydrolyzing the cGMP with a high specificity, and is widely distributed in human bodies (J Bio Chem, 1998, 273(25) 15559-15564). A PDEIX inhibitor is capable of inhibiting the enzymolysis effect on the cGMP by the PDEIX, and thus improving the cGMP level. In this way, the effects of NO and insulin are magnified, and the effects of dilating arteries are exerted, metabolization is speeded up, and atherosclerosis is resisted (WO03037432). Researches show that the cGMP plays an important role on the improvement of the cognitive ability of the human being. These characteristics render the phosphodiesterase IX to be a new target spot for the treatment of diabetes, obesity and cardiovascular diseases, and for the improvement of attention, cognitive abilities, learning and memory.
In 2005, Frank Wunder (Mol Pharmacol, 2005, 68: 1775-1781) reported the first PDEIX selective inhibitor BAY 73-6691. This discovery promotes people's commitments on research into the PDEIX selective inhibitor. The phosphodiesterase IX inhibitors discovered in recent years have better phosphodiesterase IX and achieve better pharmacological activity. International Patents WO2003037899, WO2004096811, and WO2012020022 have disclosed a pyrazole pyrimidine ketone-parented PDEIX inhibitor and a process for preparing the same; WO2004113306 has disclosed a cyano pyrimidine ketone-parented PDEIX inhibitor and a process for preparing the same; WO2004096811 and WO2012040230 have disclosed an imidazole trinitrogen heterocyclic ketone-parented PDEIX inhibitor and a process for preparing the same; WO2012004900 has disclosed a thienopyrimidine-parented PDEIX inhibitor and a process for preparing the same; WO2012033101 and WO201203314 have disclosed an imidazo quinoline ketone-parented PDEIX inhibitor and a process for preparing the same; and WO2004096811 has disclosed a PDEIX inhibitor using other ketone compounds as a matrix and a process for preparing the same, wherein the ketone compounds comprise imidazolyl pyrimidine ketone, oxazole pyrimidine ketone, and thiazole pyrimidine ketone. In 2011, our research group disclosed a 6-position-N-substituted pyrazolo pyrimidine ketone-parented PDEIX inhibitor having better inhibition activity and a preparation process thereof (CN102260266A).